Efficiency Starts with Good Design

I've had a few people lately tell me they want to get their electricity for their new home from renewable energy. When I ask them what kind of power system they want to build some of them tell me,"We're not sure yet, we want to get the house built first." I like to think of this as putting the cottage before the horsepower.

Planning for a renewable energy system should begin at the same time you decide to build your house. By carefully considering the impact renewable energy will have on your life you can build in features that can best take advantage of it.

Design your house to have plenty of sunshine. If at all possible, build a passive solar design to take advantage of the sun for heat as well as power. A good passive solar design will not add to the cost of your home and will save you money in the long run.

According to Christopher Alexander, author of the book A Pattern Language, all rooms in a house should have natural light from two directions. He means this as a design technique that makes a home more comfortable to the occupants. In a well designed renewable energy building this also means that the rooms don't need artificial light during the day.

I recommend Alexander's book to anyone seriously considering designing and building their own home. His insights and suggestions will have a profound impact on your design and will fit in well with alternative energy choices.

The decision to use renewable energy will affect how you heat your home, pump your water, and how you refrigerate and cook your food.

For home heating, avoid any heating system that takes electricity to run fans or large pumps. It should go without saying that you never want to use electric baseboard heat. Passive solar heat with a woodstove backup works well, as does radiant floor heat. Radiant floor systems require only a small boiler or on-demand water heater and a low voltage pump to move hot water through pipes in or under your floors.

Good use of insulation and/or thermal mass (in a passive solar home) can also reduce the electricity consumption of your heating system. A home using thermal mass will have a quantity of concrete, stone, or even water filled barrels designed into the home and exposed to the sun. This "mass" will absorb heat from the sun during the day and release it slowly during the night.

Water pumping can consume the largest amount of electricity in a rural home. The standard system generally uses a large 120vac or 220vac pump placed in the bottom of the well. This large pump runs whenever the pressure in the home water system drops below a certain set point. These pumps consume large amounts of electricity, especially when starting.

Whenever possible you need to pump your water with low voltage DC pumps rather than large energy hogging AC pumps. You can use DC pumps if you have a well that has a "static water level" (SWL) of 100 feet or less. The static water level in a well is the distance from the surface of the ground to the surface of the water in the well. This is different from the well depth.

For example, our well is 260' deep but has a SWL of only 60'. We use a 24 volt Shurflo submersible well pump that pumps at about 2 gallons a minute. This pump runs into a 1200 gallon cistern buried next to the house and runs about once a week for a few hours. We then draw water from the cistern using a 24 VDC pressure pump that pressurizes the house water system to a standard 50 psi.

These two pumps together use less energy in a week than a standard well pump would use in a day. However if your SWL is too low or your well is too far from the house it may be necessary to consider using a generator to power a standard well pump to fill a cistern and then use the low voltage pressure pump for daily use. You can then incorporate the generator into your energy system to provide backup power.

There are two approaches to refrigeration that are commonly used in renewable energy homes. Propane or natural gas refrigerators and high efficient electric (either ac or dc) refrigerators. Gas refrigerators can be expensive and are generally fairly small. For a small home they can be practical but you still have to buy the gas. High efficient electric refrigerators are also expensive (with one exception) and add some cost to your electric system for the additional capacity needed to run them.

We use a refrigerator called the Vestfrost. Made in Denmark, it is the cheapest of the high efficiency refrigerators available. Though not the most efficient, it more than makes up for it in lower cost. Even with the need for an additional PV panel it still cost us less than the most efficient refrigerator on the market. In two years of operation it hasn't given us a single problem or a had a negative impact on our power system.

For cooking you need to use some form of gas or a wood cook stove (for the traditionalists). And not just any gas stove will do. The gas stove manufacturers have added all sorts of fancy features to their stoves. Piezoelectric igniters for stovetops, glowplug igniters for ovens, self-cleaning ovens, electric clocks, lights, all the fancy bells and whistles. And they all use electricity, lots of it.

But some careful shopping can get you good quality standing pilot gas stove that uses no electricity. The simplest way to find them is to go to the showroom and look at the back of all the gas stoves. If you see a power cord coming out of the back, don't buy it. All suppliers carry standing pilot ovens, you can generally find them in the back of the showroom or the last few pages of the catalog.

Which leads me to the topic of phantom loads. In the next column I will describe how good design can eliminate these pesky critters and save on system costs.

All Contents © 1997
Wagonmaker Press
Thomas W. Elliot


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